JPH0463325B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Field and Background of the Invention The present invention relates generally to mass flow metering technology, and more particularly, to mass flow metering techniques, in which
The present invention relates to a new and useful mass flow metering device and method using a main tube. These tubes are oscillated between fixed points to impart reciprocating angular rotation to the tubes.

Devices are known that utilize the effects of angular motion of a flowing fluid to directly measure mass flow. For example, U.S. Patent No. 2,865,201 and U.S. Pat.
See No. 3,355,944 and US Pat. No. 3,485,098.

U.S. Pat. No. 4,109,524 describes an apparatus and method for metering mass flow through a conduit by reciprocating a section of the conduit such that the section undergoes longitudinal angular rotation. has been done. The section has a linkage for reciprocating it and for measuring the force exerted on the section which is based on the apparent force generated by the mass flow through the section. Concatenated. Direct metering of mass flow rate is thus obtained in such embodiments.

A method of measuring mass flow rate using such force will be described with reference to FIG. Figure 1 shows X, Y, Z
shows a vector array in the coordinate system of

Mass flow rate m that flows with velocity vector
A force that causes an angular velocity about an axis to
When Fc acts, the force is observed as c=2m×.

If the fluid carrying tube, designated 10 in FIG. 1, is rotated in the c-plane in a clockwise direction as indicated by arrow 12, an angular velocity as shown in FIG. 1 will result. However, if the conduit 10 is
If it is not rotated in one direction as shown by 2, but is swung back and forth about the pivot shown as 16, the magnitude and direction of the angular velocity will also be swung, and therefore the magnitude and direction of force c will be swung proportionally. move.

The displacement vector at any point along the tube, such as point 14, can be represented as lying only along the axis for small amplitudes. Therefore, the tube 10 is
When it is oscillated about its own pivot point 16 with extremely small amplitude by a sinusoidally vibrating driving body, the displacement velocity and the magnitude of the acceleration vector at a point 14 far from the pivot point 16 are as follows. This is represented by the graph shown in Figure 2. The displacement at point 14 along the axis is indicated by solid line 20. The velocity v at point 14 is indicated by a dash-dot line 22. The unit here is inches/second, which is
Represents dy/dt.

Acceleration A is shown as a solid line 26, which represents the second derivative of displacement with respect to time. Its units are inches/second ² , which represents d ² y/dt ² .

As the fluid flows through the tube, a force c=2m× acting on the mass flow rate is also generated. According to Newton's third law, equal and opposite forces are generated acting on the tube itself and related to the acceleration A'. -c and ' are the forces occurring along the axis. The magnitude of acceleration' is indicated by dashed line 28. From the definition of force -c mentioned above, this force is out of phase with the acceleration based on the driving force applied to the conduit.
It will be understood that the 90° difference is proportional to the velocity of point 14. The resultant force acting on point 14 is the sum of these driving forces and force -c, which are 90° out of phase. The dashed line 24 indicates the driving force and the force -
It represents the total value of acceleration and ′ which is proportional to the sum of Fc. Therefore, the phase difference φ between the acceleration of the original driving force and the resulting acceleration is a direct measure of the force -c, which is directly proportional to the mass flow rate.

If the driving force is sinusoidal, its displacement,
Velocity and acceleration are similarly sinusoidal, and their phases differ by 90° and 180°, respectively. This ensures that the phase difference φ is the same regardless of whether it is measured in terms of displacement, velocity, or acceleration function of the driving force relative to the resultant force of the driving force plus force -c.

SUMMARY OF THE INVENTION In accordance with the present invention, a pair of parallel conduits are fixedly supported at both ends and disposed in side-by-side relationship. At the center of the conduits and in the portions between them, drive means are provided for applying lateral oscillations to the conduits that repeatedly draw the conduits towards and away from each other.
This oscillation is made possible by the flexibility of the conduit and the fact that both ends of the conduit are held in fixed positions.

A sensor is provided on each side of the drive means and approximately midway between the drive means and the support on each side. These sensors generate signals corresponding to the velocity of the conduit at the location of the sensor. Fittings and passageways are arranged in the support for providing mass flow. The mass flow is divided approximately equally into two conduits through one support, then recombined and delivered out the other support.

When no fluid flows through the conduit, the frequency of the oscillation of the drive means exactly matches and is in phase with the frequency of the oscillation detected by the two sensors. However, when mass flow flows through a conduit, all sensors continue to detect the same frequency as the drive frequency, and the phase of the drive frequency at the upstream sensor in the direction of mass flow is lag, while the phase of the drive frequency at the downstream sensor advances. These phase leads and lags can be used directly as a measure of the mass flow rate through the conduit.

OBJECTS OF THE INVENTION It is therefore an object of the present invention to provide a device for measuring the mass flow rate of a fluid, comprising a pair of parallel conduits having opposite ends, a longitudinal length and a center point, and a device for measuring the mass flow rate of a fluid. It consists of a support body for supporting the conduit in a fixed state, and a drive means for swinging the intermediate portions of both ends of the conduit in a direction transverse to the longitudinal direction,
Coupling means are provided on the support means for supplying fluid to the conduits and distributing the fluid flow substantially equally to each conduit, and further includes at least one variation at a location spaced from the center point and spaced from each end. The object of the present invention is to provide a device in which a quantity detection sensor is provided. A sensor that detects the amount of variation can detect displacement, velocity, or acceleration. The phase difference between the detected motion value and the drive motion value is a measure of the mass flow rate of the fluid flowing through the conduit.

Another object of the invention is to provide a drive means at the center point of the conduit and a pair of sensors on each side of the center point, the upstream sensor delaying the phase of the drive force;
The object of the present invention is to provide a device in which the phase of the driving force is advanced by a sensor on the downstream side, and such phase advance and lag become the basis of the measured value of the mass flow rate.

Another object of the invention is to provide a device for metering mass flow that is compact, robust and inexpensive to manufacture.

Another object of the present invention is to provide a method for metering mass flow that utilizes the phase difference between the detected fluctuations of a swinging parallel conduit and the swinging force applied near the center point of the pipe. It lies in providing the following.

DESCRIPTION OF THE PREFERRED EMBODIMENT Please refer to FIG. The embodiment of the invention shown here consists of a device for mass flow metering supplied to the inlet fitting 30. The inlet joint 30 is
It is connected to a first support 32 which fixes the ends 34 and 35 of a pair of conduits 36 and 37. A Y-shaped passageway 38 directs the mass flow into the inlet fitting 30 by 2
defined within a first support 32 for splitting into two generally equal branch streams. Half of the mass flow is in conduit 3
6 and the remaining half is distributed to conduit 37.

Conduits 36 and 37 have their other ends 4 connected respectively to a second support 40 carrying an outlet fitting 44.
2 and 43. Another Y-shaped passage 46
is defined in second support 40 for recombining the flow rates of conduits 36 and 37 and directing them to outlet fitting 44 .

A drive mechanism 48 is provided between conduits 36 and 37 and near the center of the conduits. Drive mechanism 4
8 includes, for example, a solenoid coil 54 fixed to the conduit 36 and a permanent magnet 52 reciprocating within the solenoid coil 54 and fixed to the conduit 37. By applying current at a selected frequency to solenoid coil 54, conduits 36 and 3
7 can be caused to swing toward and away from each other in the vertical direction.

In FIG. 4, which is a schematic diagram of FIG.
6 and 37 are represented by straight lines. The maximum amplitude at which the conduits separate from each other is shown by solid lines 36a and 37a. The amplitude at which the conduits are closest to each other is shown by dotted lines 36c and 37c, and the rest position is shown by dash-dotted lines 36b and 37b.

Referring again to FIG. 3, conduits 36 and 37 are provided with a pair of sensors 56 and 58 spaced apart from each other and positioned on each side of drive mechanism 48. Sensor 56 includes a permanent magnet 62 magnetically coupled to a coil 66 coupled to conduits 37 and 36, respectively. Similarly, sensor 58
are coils 7 coupled to conduits 37 and 36, respectively.
It has a permanent magnet 72 that can reciprocate within 6.

By rocking conduits 36 and 37 in the manner shown in FIG. 4, sinusoidal currents are induced in coils 66 and 76. These signals are proportional to the velocity of the conduits approaching and away from each other at each sensor location.

When fluid does not flow in the conduits 36 and 37,
The oscillations applied by drive mechanism 48 to the center points of conduits 36 and 37 produce signals at sensors 56 and 58 that are in phase with each other and with the speed of drive mechanism 48.

However, when fluid flows through conduits 36 and 37, a phase difference occurs between sensors 56 and 58.

Sensor 56 generates a speed signal that lags the speed of drive mechanism 48 , and sensor 58 generates a speed signal that advances the speed signal of drive mechanism 48 .

A device, generally indicated at 80 in FIG. 3, is coupled to the sensors 56 and 58 as well as to the drive mechanism 48, or at least its power source, for measuring the lag in the respective velocity signals. The phase retardation with respect to the speed of the drive mechanism is directly related to the mass flow rate through conduits 36 and 37.

FIG. 5 is a schematic diagram of one of the conduits. One position of the sensor is indicated by point "0". This position is
The distance from the nearest support for the conduit is the point r.

At this point "0", the maximum upward amplitude of the conduit is +A and the maximum downward amplitude is -A.

In the analysis described below, the displacement from point "0" is indicated by the symbol y.

The displacement y from the rest position for any point on the conduit while the conduit through which the fluid flows is caused to oscillate in simple harmonic resonance with the maximum amplitude A is given by:

y=A sin wt...(1) here, y = displacement from rest position A = maximum amplitude w=2πf f=resonant frequency t = time (t is θ at the start of swinging.) represents.

Since the conduit is fixed at both ends and movable only transversely to its longitudinal axis, the displacement y occurs in the vertical direction. Therefore, the velocity in the vertical direction at point "0" is expressed as v=dy/dt=wA cos wt...(2), and the acceleration is a=dv/dt=d _U2 y/dt _U2 =-w _U2 A sin wt ...(3) It is expressed as follows.

The force − _c (vector) acting on point “0” is
Similar to the induced rocking motion, it moves up and down according to the following equation:

− _c = −2m _c × _c ……(4) where − _c = apparent force resulting from angular effects on the flowing fluid.

m _c = mass of fluid flowing through point “0” _c = angular velocity of point “0” = |/r|, that is, (
=×) _c = Represents the velocity of the fluid flowing through the point “0”.

If the spring constant of the conduit at point "0" is k, the amplitude of the induced rocking force is expressed as ||=-ky=-kA sin wt (5).

Since the two forces act in the same direction, their magnitude is F−F _c = | | + | − _c | = (−2m _c v _c v/r) + (−kA sin wt)
...(6) are directly summed.

From v=wA cos wt, F−F _c = (−2m _c v _c /r) wA cos wt −kA sin wt ……(7).

m _c , r, v _c , w _U2 and A are all constants for a constant mass flow rate, so if B ₁ = -2wAm _c v _c /r, B ₂ = -kA, then F - F _c = B ₁ cos wt＋B ₂ sin wt...(8)

The total value of B ₁ cos wt + B ₂ sin wt shown in equation (8) is, if γ = (B _U21 + B _U22 ) and β = tan _U-1 (B ₁ /B _U2 ), then B ₁ cos wt + B ₂ sin wt = γ sin (wt + β) ...(9).

Equation (9) mathematically expresses that the resultant force at point "0" is the same as the two resonance amplitudes B ₁ cos wt and B ₂ sin wt for driving, but the phase difference is β. ing.

Here, β=tan _U-1 (B ₁ /B ₂ )=tan _U-1 (−2wAm _c V _c /−kAr) ...(10) or β=tan _U-1 (2wm _c v _c /kr ) ...(11).

Since w = 2πf, f is the frequency of oscillation held constant at the natural resonance frequency of the conduit, r is a fixed distance, and k is a constant, α = kr / 4πf. For example, β=tan _U-1 (m _c v _c /α) ...(12) Therefore, if m _c v _c = mass flow rate, m _c v _c = α tan (β) ... (13 ) becomes.

Therefore, the force acting on point "0" is sinusoidal like the driving force, has the same frequency, and differs only in phase by β. The phase of a function of displacement, velocity or acceleration (as well as any further derivatives thereof) is also of the same magnitude for the corresponding driving force, i.e. if n is an integer, then β±n _U 〓/ 2 They differ by...(14).

For small phase differences, equation (12) becomes β=tan _U-1 (m _c v _c /α) m _c v _c /α = m _c v _c (4πf/−kr) ... ).

In order to eliminate the frequency-dependent factor f, it is necessary to consider two signals whose phases, expressed in amplitude as a function of time in FIG. 6, differ by φ.

Their frequencies are equal, and their period is T=1/f...(16) where T=period=2( _t1 + _t2 )...(17). The associated phase angle β is then defined as β=πt ₁ /(t ₁ +t ₂ )=2πt ₁ f (18).

If equation (18) is substituted into equation (15), β=m _c v _c (4πf/kr)=2πt ₁ f (19). Therefore, m _c v _c = mass flow rate = (kr/2) t ₁ ...(20).

In equation (20), the value dependent on the frequency is eliminated,
Only a known spring constant, length r and time difference t ₁ are required. The time difference t ₁ can be measured using an oscilloscope and standard laboratory equipment.

In any given setting, k and r are constants, so the magnitude of the time difference t ₁ is directly proportional to the mass flow rate. The time difference t ₁ can be measured along any straight line that crosses the signal waveform as shown in FIG.
It is clear that the coordinates are not limited to the origin.
The time difference t ₁ can be found at any two points in time using equal first and second derivatives between any period of the two signals, regardless of the gain, i.e. the residual deviation of the DC. .

In this embodiment, the above measurements are made at point "a" on one side of the parallel conduits of FIG.
Mass flow rate can be measured directly by measuring the time difference t ₁ between point "u" of the induced signal and point "a" of the signal caused by the mass flow rate.
In the embodiment of FIG. 3, the signal lags at point "a" than at point "u." Similarly, at point “b”, point “x”
later, at point "c" it is ahead of point "u" and at point "d" it is ahead of point "x". (The phase angle amplitude is equal at all these points, being a positive number at the leading point and a negative number at the lagging point.) Thus, the points "a" and "b" where the signal lags, and the points where the signal advances. The total phase difference φ between "c" and point "d" provides a signal that samples the total mass flow rate as a twice weighted average of both conduits. Thus, the sum of the phase angle leads and lags cancel out and provide the resonant frequency data necessary to maintain the conduits at their natural resonant frequency regardless of changes in pressure, density, or temperature.

In the parallel conduit configuration shown in FIG. 3, both halves of drive mechanism 48 and both sensors 66, 7
6 can also be attached directly to conduits 36 and 37 to reduce common mode vibration noise and improve efficiency. (The sprung masses at points "a,""b,""c," and "d" are equal, and the sprung masses at points "u" and "x" are also equal.) The advantages are described below:2
Direct metering of mass flow proportional to the measured time difference between two points using equal first and second derivatives between any period of two equal frequency signals, simple and robust construction. It is easy to assemble, it is small overall, it is easy to integrate, it has nothing to do with fluid density, it has little relation to temperature, it is easy to change the size, and it has nothing to do with fluid viscosity. It is applicable to liquids, gases and slurries.

In an alternative embodiment, a phase measuring device is provided, designated by the numeral 80 in FIG. One example is the Heuretsu Pats Card Model 3575A. The phase difference from the drive position to a detection point near and spaced from the center of the conduit can be used to measure mass flow rate. Accuracy is improved by placing sensors on both sides of the drive mechanism.

Although the present invention has been described above based on embodiments, it should be noted that many changes can be made within the present invention.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram of a coordinate system in which a conduit for carrying a mass flow rate can be rotated, illustrating the generation of force _c . FIG. 2 is a graph showing various characteristics of the fluctuations and forces experienced by the conduit of FIG. 1 at a certain point. FIG. 3 is a cross-sectional view of one embodiment of the present invention. FIG. 4 is a conceptual diagram of the fluctuations that the conduit of the present invention undergoes. FIG. 5 is a schematic diagram showing the maximum amplitude of an oscillating conduit. FIG. 6 is a graph showing two sinusoidal curves having the same frequency but different phases at a time difference _t1 . The names of the main parts in the figure are as follows. 30
...Inlet joint, 32...First support, 36,3
7... Conduit, 40... Second support, 44... Outlet joint, 48... Drive means, 56... First sensor, 58... Second sensor.

Claims (1)

Claims: 1. An apparatus for metering the mass flow rate of a fluid stream, wherein each conduit has opposite ends and a longitudinal length and a center point between said ends, each conduit receiving approximately half of the fluid flow. a pair of parallel conduits, a support means connected to the conduits for holding the ends in a substantially fixed position; and a fluid to be metered for mass flow into the pair of parallel conduits. coupling means connected to said support means for providing said conduits with said conduits at a selected frequency in a direction transverse to their respective longitudinal directions substantially about their center points; , drive means associated with the conduit; at least one first sensor for detecting vibrations in the conduit at a first detection point spaced from each center point and opposite ends; and a second sensor for detecting at a second detection point spaced apart from each center point and on the opposite side of the first detection point on one side of each center point, a first detection point upstream of each center point with respect to the direction of fluid flow; a second detection point downstream of each center point with respect to the direction of fluid flow; the phase of the fluctuation at the point lags the selected frequency, the phase of the fluctuation at the second detection point leads the selected frequency, and the phase lag corresponds to the mass flow rate of the fluid flow. A device for measuring the mass flow rate of a fluid stream. 2. The driving means includes a solenoid coil coupled to the center point of one of the pair of conduits, a permanent magnet coupled to the center point of the other of the pair of conduits and movable within the solenoid coil, and a permanent magnet that oscillates the conduit. 2. The apparatus of claim 1, further comprising current means coupled to said solenoid coil for applying a current of a selected frequency to said solenoid coil to cause said solenoid coil to move. 3 a first detection coil in which a first sensor is coupled to the first detection point of one of the pair of conduits;
a first sensor permanent magnet coupled to the other of the pair of conduits, and a second sensor coupled to the second detection point of one of the pair of conduits; , and a second permanent magnet coupled to the other of the pair of conduits. 4 phase measuring means coupled to the first and second detection coils and solenoid coils of each conduit to determine the phase retardation of the vibrations at the first and second detection points relative to the selected frequency; 4. A device according to claim 3, comprising means for measuring the speed. 5 a support means is coupled between a first support comprising an inlet fitting for receiving fluid flow and between said inlet fitting and the first end of each conduit for diverting fluid to each conduit; 5. The apparatus of claim 4, further comprising a Y-shaped passageway in said first support. 6. The support means comprises a second support having an outlet fitting for receiving fluid flow from the conduit and within said second support coupled between the second end of the conduit and said outlet fitting. 6. A device according to claim 5, further comprising another Y-shaped passageway defined in the . 7. The phase difference between the fluctuations detected at the detection point and the selected frequency of oscillation to cause the conduit to oscillate substantially at its respective center point, resulting in a measured value of the mass flow rate of the fluid flow. 2. Apparatus according to claim 1, comprising detection means for measuring coincident phase differences. 8 A method for measuring the mass flow rate of a fluid stream, the method comprising: determining the center point of a pair of parallel conduits transversely across the conduit at a selected frequency while keeping the ends of the conduits substantially fixed; oscillating, passing approximately half of the fluid flow whose mass flow rate is to be measured through each conduit, and detecting fluctuations in each conduit at a first detection location spaced from the center point of the conduit and from opposite ends of the conduit; detecting at the center of the conduit; and measuring a phase difference between a selected frequency of oscillation at the center point and the measured fluctuation at the first detection location; a first point away from the point and at the center point;
at the second detection position opposite to the detection position of
detecting fluctuations in the conduit at a second detection position also spaced from both ends of the conduit; and combining the fluctuations at said second detection position with a selected frequency of oscillation at said center point. and measuring a phase difference between the selected frequency of oscillation at the center point and the measured fluctuation at the first sensing position of the fluid. a mass flow rate of the fluid flow, and a phase difference between a fluctuation at said second sensing position and a selected frequency of oscillations at said center point also corresponds to a mass flow rate of the fluid flow. A method for metering the mass flow rate of a fluid stream, characterized in that: